1io_uring_prep_read(3)           liburing Manual          io_uring_prep_read(3)
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NAME

6       io_uring_prep_read - prepare I/O read request
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SYNOPSIS

9       #include <liburing.h>
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11       void io_uring_prep_read(struct io_uring_sqe *sqe,
12                               int fd,
13                               void *buf,
14                               unsigned nbytes,
15                               __u64 offset);
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DESCRIPTION

18       The  io_uring_prep_read(3)  prepares an IO read request. The submission
19       queue entry sqe is setup to use the file descriptor fd to start reading
20       nbytes into the buffer buf at the specified offset.
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22       On files that support seeking, if the offset is set to -1, the read op‐
23       eration commences at the file offset, and the  file  offset  is  incre‐
24       mented  by the number of bytes read. See read(2) for more details. Note
25       that for an async API, reading and updating the current file offset may
26       result  in unpredictable behavior, unless access to the file is serial‐
27       ized. It is not encouraged to use this feature,  if  it's  possible  to
28       provide the desired IO offset from the application or library.
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30       On files that are not capable of seeking, the offset must be 0 or -1.
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32       After  the  read  has been prepared it can be submitted with one of the
33       submit functions.
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RETURN VALUE

37       None
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ERRORS

40       The CQE res field will contain the result of the operation. See the re‐
41       lated man page for details on possible values. Note that where synchro‐
42       nous system calls will return -1 on failure and set errno to the actual
43       error value, io_uring never uses errno.  Instead it returns the negated
44       errno directly in the CQE res field.
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SEE ALSO

47       io_uring_get_sqe(3),  io_uring_prep_readv(3),  io_uring_prep_readv2(3),
48       io_uring_submit(3)
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52liburing-2.1                   November 15, 2021         io_uring_prep_read(3)
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